👔(backend) add Organization model

We introduce the Organization model has a "hat" for all
users and team.

Each User must have a "default" organization.
Each Team must have an organization.

When a User creates a new Team, the team is linked to their
default Organization.

For now the Organization should not be visible to end users
this is a purely technical aspect as it.

The models are also adding a permission to allow User to edit
an Organization, but for now there are no endpoints for that.

Next steps:
- Add an Organization to each User and Team on all environments
  to mark Organization as mandatory in database.
- Add scope to Organization to list the Service Provider list
  allowed for a User in an Organization.
- Add endpoints + frontend to manage Organization's scopes

src/backend/people/settings.py

@@ -388,6 +388,11 @@ class Base(Configuration):
         environ_name="USER_OIDC_FIELDS_TO_NAME",
         environ_prefix=None,
     )
+    OIDC_ORGANIZATION_REGISTRATION_ID_FIELD = values.Value(
+        default=None,
+        environ_name="OIDC_ORGANIZATION_REGISTRATION_ID_FIELD",
+        environ_prefix=None,
+    )
 
     OIDC_OP_TOKEN_INTROSPECTION_ENDPOINT = values.Value(
         None, environ_name="OIDC_OP_TOKEN_INTROSPECTION_ENDPOINT", environ_prefix=None
@@ -437,6 +442,15 @@ class Base(Configuration):
         environ_prefix=None,
     )
 
+    # Organizations
+    ORGANIZATION_REGISTRATION_ID_VALIDATORS = json.loads(
+        values.Value(
+            default="[]",
+            environ_name="ORGANIZATION_REGISTRATION_ID_VALIDATORS",
+            environ_prefix=None,
+        )
+    )
+
     FEATURES = {
         "TEAMS": values.BooleanValue(
             default=True, environ_name="FEATURE_TEAMS", environ_prefix=None
@@ -599,6 +613,15 @@ class Test(Base):
     # this is a dev credentials for mail provisioning API
     MAIL_PROVISIONING_API_CREDENTIALS = "bGFfcmVnaWU6cGFzc3dvcmQ="
 
+    ORGANIZATION_REGISTRATION_ID_VALIDATORS = [
+        {
+            "NAME": "django.core.validators.RegexValidator",
+            "OPTIONS": {
+                "regex": "^[0-9]{14}$",
+            },
+        },
+    ]
+
 
 class ContinuousIntegration(Test):
     """